EMOZIII — Emoji Substitution Cipher

Platform: spbctf | Category: Crypto | Type: Challenge | Difficulty: Medium | OS: NA | Author: XESXOR | Date: 2026-03-08 | Status: Solved Techniques: emoji_substitution_decryption, frequency_analysis, known_plaintext_attack

Summary

Task: Decode emoji-encoded text where each emoji represents a letter. Solution: Known plaintext attack using flag format spbctf{ to build initial mapping, then frequency analysis for remaining letters.

EMOZIII — Crypto Kids 2.0

Description

Russian text "Вы что там совсем поехали кукухой?" (Are you completely crazy?) with emoji-encoded file.

Analysis

Each unique emoji represents a letter of the English alphabet. Total of 28 unique emojis (26 letters + symbols). Using known plaintext attack with flag format "spbctf{" to build the initial mapping table.

Solution

 python read-only • copy allowed Copy
#!/usr/bin/env python3
# Step 1: Find pattern spbctf{ in emoji text
# Step 2: Build mapping emoji → letter
# Step 3: Apply frequency analysis for remaining letters
# Step 4: Decode the entire text
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# Solution structure example:
def decode_emoji_cipher(emoji_text, known_pattern="spbctf{"):
    # Find sequence of 7 unique emojis
    # that corresponds to pattern spbctf{
    
    mapping = {}
    # After analyzing text about SPbCTF community
    # find the flag in the text
    
    return "spbctf{REDACTED}"

# Text tells about SPbCTF community
# Flag found in text: spbctf{REDACTED}
print("Flag: spbctf{REDACTED}")

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